Sunday, October 17, 2010
Saturday afternoon I took the kayak up to Everett and paddled across to Jetty Island. In the summer, the City runs a ferry over to the island and the main beach on the west side fills up with people enjoying the warm (relatively) water flooding in over the broad sand flats, but on this trip I had the whole place to myself.
The tide was high, so there wasn't much beach to walk on (and the upland portion of the island, at least the north end, is North America's densest thicket of Himalayan blackberry). I walked up to the northeastern tip of the island,
which was littered with remnants of old structures and lots of big wood, washed down the river and stranded on the beach. Then I wandered back to the main beach, the spit, and the lagoon.
Everett is located just south of the mouth of the Snohomish River (as was the historic Tulalip community of Hibulb, long before Everett Colby's father founded the city). The shallow subtidal foredelta of the river extends out into Port Gardner, making deep water access difficult, so a century ago, a jetty (training structure or breakwater?) was constructed to channel the main stem of the river southward along the waterfront (see the aerial photo linked to the title of this post). Dredged sand was placed on the western side of this structure and gradually a new island was built. In 1989, the Port of Everett used the dredged material to create an artificial berm - basically a spit, that in turn formed a large tidal lagoon.
Jetty Island is a Puget Sound anomaly. It is all sand, river sand, unlike most of our gravelly beaches, which get their sediment from eroding bluffs and small, steep streams. It is completely artificial - this entire area was shallow sand flats historically. And it is the largest beach nourishment project on the Sound and the only one built from dredged river sand. It is a frequently cited example (particularly by the Corps) of beneficial use (of dredged sediment).
Some folks note that the ecological picture painted at Jetty Island isn't really true restoration (they're right). Others seem more put off by the blackberries and invasive species than they are impressed by the salt marsh and the birds. And some people are just leery of pretty much everything the Corps of Engineers does (not an unwarranted skepticism). But ultimately, this is a pretty neat place. Maybe they ought to build something like this outboard of the Shilshole breakwater or along a section of the railroad grade!
Sunday, October 10, 2010
This is a little out of order - I managed to skip over it when posting other entries last week. These shots go back about two weeks.
The Elwha River drains the northern interior of the Olympic Mountains, arriving at the coast in a gravelly delta a few miles west of Port Angeles. The river mouth shifts around, although maybe not as much as it did before the levees were built in the lower valley - including one immediately west of the mouth that has recently been raised. The mouth is a complex set of coarse gravel spits, bars, and islands and a number of small lakes and lagoons.
The delta projects well out into the Strait of Juan de Fuca where it is influenced both by waves and swell from the west, as well as storm waves from the northeast. The beach on the western side, facing Freshwater Bay, is a broad crescent and longshore transport may be fairly balanced (aerial view). On the eastern side, however, the beach that fronts the delta is eroding rapidly and sediment is moved eastward down the coast towards Ediz Hook in Port Angeles (previous posts on this stretch of shoreline).
The Elwha's two high dams are supposed to start coming out next year. It may be some time before the gravel behind the dams shows up at the coast, but maybe the delta will see more immediate changes due to differences in flood events or the release of fine sediment. This is going to be a neat place to watch over the next decade.
Thursday, October 07, 2010
I titled this post "Pioneer" since that's what the sign along the railroad calls it - and since Pioneer was the major operator of the huge gravel pits that marked this site for the most of the 20th century. I could have called it Chambers Creek, since it lies just north of the creek and because the whole place is now managed as "Chambers Creek Properties", including its brand new premier golf course. But I'd rather reserve that title for the Creek itself - which I have (Chambers Creek-2008).
The 200' gravel-rich bluffs once reached to the Sound (historical photo), but they were excavated back a kilometer to help build Seattle and Tacoma and all the roads that connect them. Now there is a rolling reclaimed landscape - part treatment plant, part park, and of course, part golf course. The railroad still runs along the shoreline, but there is now a new overpass connecting the park to its two mile long beach. Or at least two miles when the tide isn't too high, since there are places it runs up against the railroad riprap at high tide.
Sequalitchew Creek is trapped in a narrow ravine between the former Dupont munitions plant (now Northwest Landing, a large planned development, and its golf course) and the big still-operating gravel pit to the north. The original Fort Nisqually (established in 1833 by the Hudson's Bay Company and the first European settlement in Washington) was located on this creek.
The creek empties into the Sound just north of the Nisqually Delta through a small estuary, or at least it did prior to the Northern Pacific building a railroad along this shoreline in the late 1800s. The creek now reaches the beach through a small box culvert below the mainline from Seattle to Portland. A small marsh remains trapped in the valley above the railroad embankment.
A narrow gauge rail line used to serve the munitions plant, running down the ravine, passing under the mainline, and out to a pier (long unused, but only recently removed). You can walk down the old grade to the marsh, through the short tunnel, and then emerge suddenly, and spectacularly, at the beach and the Sound.
The road was probably built on the back of the beach a century ago. Sea level is probably 20-25 cms higher since then, and the big house on the artificial point just north has trapped any sediment originally destined to rebuild this beach, so the road was getting undermined.
They could have dumped rock - such an easy, cheap, ugly, and often not completely successful solution. But instead, they tried anchoring logs on the beach face and reinforcing the soils on the bank with geofabric. I don't know the whole story here, but I wish we had the resources to monitor more of these (other than brief visits while racing to the late afternoon ferry). We could actually start to learn something. And then we could tweak the design, not just bury it under riprap next winter when the storms roll in.
I believe the logs are intended to act like sills and help perch a slightly higher beach behind them, reducing wave action at the bank. Sometimes this approach works, but often it does not, with beaches rising and falling as if they are oblivious to the logs' intended role. Here, I don't think the logs have hurt, I'm just not sure they've added much.
The geotextile is "softer" than riprap and allows for planting if it doesn't unravel, but it has neither the resistance to erosion (and floating logs) of something more durable, nor the ability to act like a natural gravel berm. I suppose a more substantial gravel berm might have been worked a little better here, although there might still have been need for some structural elements and some occasional maintenance - in the form of a truckload of sandy gravel every couple of years. But ultimately, there just isn't much room to work where the beach is narrowest. These sites are never easy.
Boat ramps are notorious for acting like groins and for paving over viable beach habitat. It's hard to bury one's eggs in concrete. So in several places on the Sound, new ramps have been built like this, bridging over the beach. Others can be found in Allyn, Silverdale, and a few other spots. Like any bridging structure or pier, they can trap drift logs and then they begin to act like groins - which means some maintenance is required. It also seems to matter how they are oriented. If wave action is oblique, it is more likely to transport sediment under and past the structure. But if wave action is more normal to the beach, sediment tends to accumulate beneath the structure, which shouldn't be a surprise, but sort of defeats the purpose of allowing unimpeded sediment transport.
I like this little park - it's got great views across the Sound at our local metropolis. The edge of the lawn is a little ragged, as it is built on fill and the waves want to nibble way at it, but generally it is doing fine. This is a nice little sandy beach - at least by the coarse standard of this region.
The beach on the northwest side of Clam Bay was once a spit with a lagoon tucked in behind. But the lagoon made a convenient dumping ground and became a cleanup site. It is ironic that it is also now the site of an EPA and Department of Ecology Laboratory and that there is a NOAA Fisheries lab at the head of the bay.
The site of the old lagoon was capped with clean fill, but instead of armoring the shoreline (which consisted of various nasty things corroding out of the gravel), they built a beach. The beach has adaptively managed itself a little since it was constructed, with some erosion occurring at the southeastern (updrift) end and a new berm forming farther bayward at the western end, but all in all its done quite nicely (or so it appears to this casual observer) and sure beats a foreshore covered with basalt boulders and quarry spalls.
Twanoh State Park is perched on the delta of Twanoh Creek, along the south shore of Hood Canal. The shoreline of this part of Hood Canal (not really a canal) is heavily built with homes, perhaps obscuring an interesting geologic history, since they may be built on a raised terrace resulting from late Holocene earthquakes. Various characteristics of this shoreline suggest that it was elevated at some point, or points, in the past.
The parking lot and boat ramp on the west side are built on top of the original beach (if there ever was much of one) and the stream delta. What isn't covered by pavement is covered with broken riprap, but fortunately today's tide kept that out of sight. There's a small beach, with wrack lines of oyster shell and leaves and eelgrass, just west of the ramp (and featured in one of the first posts in this blog, way back in late 2005 -- Hood Canal).
On the east side, there's a nice gravel beach swash-aligned with the maximum fetch from the east, and a long narrow lagoon that's been modified and plumbed for children (the old maps show with an inlet near the tip of the point). Discussions today were around what might be done to improve the ecology without jeopardizing either the recreational uses or the 1930s Civilian Conservation Corps landscape and historic stone structures.
We visited the site because questions have arisen about what do with the old mole (basically the term for an artificial peninsula used as a pier), which hasn't been used since the quarry shut down years ago. It was a fascinating feature, but so were the surrounding hill slopes, that were heading for the sea as fast as they could.
This stretch of shoreline along the Strait of Juan de Fuca is known for large slides and these were very impressive. The pictures show both the tilted and broken forest characteristic of active sliding and the raised beach where the toe of the landslide has pushed upward.
Marrowstone and Indian Islands are connected at their southern end by a road and a tombolo and a salt marsh. The old maps raise the possibility that there might have once been a tidal connection of some sort (and that the tombolo was a spit) and that it vanished when the road culvert cut off too much of the exchange. It's a complex site, since Kilisut Harbor (between the two islands) also has a substantial inlet at the other end. Reconnecting might be good for commuting fish and circulation in the lower bay, but it would require opening up the culverts into a bridge of some sort and reestablishing a channel through a portion of the marsh and barrier beach. Nothing is going to happen right away, but it's interesting to think about.
Sediment on this beach is transported northwestward by wave action, eventually forming the wonderful spits and lagoons at the southwest end of Indian Island.